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A contractor for the UK's National Health Service is under investigation because of a buildup in medical waste including body parts.

(CNN)A criminal probe has begun after hundreds of tons of human body parts and medical waste were allowed to build up at UK disposal sites.

Healthcare Environment Services, a disposal company contracted by the UK's National Health Service (NHS), is being investigated by the Environment Agency for being in breach of permits at five waste-management sites.

"The Environment Agency has found Healthcare Environmental Services to be in breach of its environmental permits at five sites which deal with clinical waste," an Environment Agency spokesperson said in a statement. "We are taking enforcement action against the operator, which includes clearance of the excess waste, and have launched a criminal investigation."

"We are supporting the government and the NHS to ensure there is no disruption to public services and for alternative plans to be put in place for hospitals affected to dispose of their waste safely," the spokesperson added.

Healthcare Environment Services is understood to have been monitored closely since the Environment Agency notified the government of the issue in late July. The firm removes waste from a number of -- but not all -- hospitals in England and Scotland.

The government emphasized that anatomical waste is a small portion of the what is stored by Healthcare Environment Services and that the Environment Agency has been working with the company to ensure that it is kept in refrigerated units within the confines of facilities.

"There is absolutely no risk to the health of patients or the wider public," a government spokesperson told CNN. "Our priority is to prevent disruption to the NHS and other vital public services and work is underway to ensure organizations can continue to dispose of their waste safely and efficiently."

Healthcare Environment Services told CNN in a statement that it is working to reduce the volume of waste, adding that the UK's aging incineration facilities are in part to blame for the buildup.

"Over the last year, this reduced incineration capacity has been evident across all of the industry and has affected all companies. Healthcare Environmental has been in discussion with the environmental regulators and has consistently highlighted these issues," the company said.

But the Environment Agency disagrees, saying that there is sufficient incineration capacity and that the majority of sites dealing with the disposal of clinical waste are in compliance with regulations.